The invention relates to a remote feeder reactance coil for energy input and output in signal transmission lines as well as in signal transmission systems including signal transmission lines, where intermediate amplifiers are supplied with electrical energy via said signal transmission lines.
Signal transmission systems known from practice transmit a high-frequency signal from a signal source to a signal drain via a signal transmission line, e.g. a coaxial cable. For this purpose, large distances often need to be bridged. As a result, the high-frequency signal will become attenuated even in high-quality lines, for which reason intermediate amplifiers will be required for regenerating the signal level.
In signal transmission systems of the prior art, such intermediate amplifiers may be supplied with electrical energy via the signal transmission linexe2x80x94which will eliminate the need for separate supply lines. In general, signal transmission lines of this design concept are subdivided into plural transmission sections or segments interconnected via couplers which present an as small as possible resistance to the high-frequency wanted signal. Within said transmission sections, energy is input or output via remote feeder reactance coils which constitute separation points for the high-frequency wanted signal. Consequently, the wanted signal will not become substantially attenuated at the input and output sites. However, in view of the specific design of remote feeder reactance coils there is the danger of resonances occurring at certain frequencies which will limit the useful frequency range of the signal transmission line.
Whether or not, and to what extent, resonance effects will occur depends very much on the self-resonance behaviour of the remote feeder reactance coils. For this reason, various designs have been developed in practice in which any occurring self-resonances will either be attenuated or altogether shifted to a frequency range which is uncritical for the wanted signal. For attenuating the self-resonance effects of the winding sections of remote feeder reactance coils, for example, it is known from practice to wire a remote feeder reactance coil with resistors or conductive layers. As an alternative, or commutatively to such attenuation, it is likewise known from practice to cause such a shifting of self-resonances by varying the spacing of the turns and/or of winding sections of the remote feeder reactance coil. Moreover, remote feeder reactance coils of the prior art are further known to have the turns of the reactance coil counter wound onto a common core so as to prevent the formation of any possibly resulting noise fields.
The disadvantages of the remote feeder reactance coils known from practice above all result from the fact that the self-resonances of the circuitry will strongly light the useful frequency ranges, despite the wirings and different winding types. Furthermore, the inductance values which can be reached with the known remote feeder reactance coils are limited with given volumes. Another problem is the considerable manufacturing effort, especially when such coils are wired with resistors and conductive layers since their exact dimensions and positions will be decisive of the resonance behaviour of the remote feeder reactance coil. The same is true for the variation of the windings, so that, in summary, one can say that prior art remote feeder reactance coils make maximum demands on production engineering, in view of the required precision in manufacturing.
It is the object of the invention to provide a reactionless connection of a high-frequency signal path and a low-frequency energy supply for signal transmission systems over an as broad as possible frequency range, at the same time keeping the required manufacturing effort small.
In accordance with the invention, a remote feeder reactance coil comprises a primary winding, preferably of an electrically insulated conductive material, carrying the feed current, and an attenuation circuit of a kind which has a secondary winding of a preferably electrically insulated conductive material, wherein said secondary and primary windings interact with each other through capacitive and/or inductive coupling. Providing a secondary winding of an electrically insulated conductive material is a much less complex step in manufacturing than the comparable measures of the prior art. At the same time, its presence allows very precise and effective influencing of the self-resonance behaviour of the remote feeder reactance coil since the use of a secondary winding clearly allows more positioning and design alternatives than other means of the prior art.
The use of a secondary winding allows a well-aimed intervention in the internal function mechanism of the reactance coil which results in the secondary winding undesired interactions of individual winding sections of the primary winding.
Preferably, said primary and secondary windings have substantially parallel winding axes, in particular one common windings axis. This considerably diminishes the required manufacturing effort. If any turns of said secondary winding extend between the turns of the primary winding, the turns of the secondary winding will shield the turns of the primary winding from each other. This will largely eliminate any undesired effects between individual turns of the primary winding which occur in other designs and, cumulated, will cause the disadvantageous resonance effects. If the turns of the primary and secondary windings each are wound the ones on top of the others in a radial direction, a comparatively analogous result is obtained regarding self-resonance suppression.
The possibility of varying the ohmic resistance of said attenuation circuit e.g. by means of an ohmic resistor, allows the attenuation behaviour to be influenced precisely.
The presence of the secondary winding according to the invention allows an increase both of the reproducibility and the precision of remote feeder reactance coils, at the same time leaving a lot of leeway concerning the dimensions, choice of material and wiring of said secondary winding. Another possibility is to electrically connect one end of the secondary winding to the primary winding. Furthermore, if one substitutes complex functioning circuitry for the ohmic resistor, this will allow a well-aimed influencing of the behaviour of the attenuation winding in the frequency range.